Fuel consumption calculation unit, fuel consumption measuring apparatus, and exhaust gas measuring apparatus

1. A fuel consumption measuring apparatus that measures fuel consumption of an engine, the fuel consumption measuring apparatus comprising: an exhaust gas flow path that is connected to a tail pipe of an exhaust pipe of the engine such that exhaust gas emitted from the tail pipe is introduced; a flow rate sensor that is provided in the exhaust gas flow path and measures a flow rate of the exhaust gas flowing through the exhaust gas flow path; an air-fuel ratio sensor that is provided downstream the tail pipe and a catalyst associated with the engine in the exhaust gas flow path and measures an air-fuel ratio; a related data storage part that stores related data indicating a relationship between an air-fuel ratio and exhaust gas density; and a calculation unit that changes exhaust gas density on a basis of the air-fuel ratio and the related data, and that calculates the fuel consumption of the engine with use of the flow rate of the exhaust gas, the air-fuel ratio, and the changed exhaust gas density.

2. The fuel consumption measuring apparatus according to claim 1 , wherein the calculation unit, in a case where the air-fuel ratio is included in a rich region, changes the exhaust gas density, and in a case where the air-fuel ratio is included in a lean region, uses a predetermined constant value as the exhaust gas density.

3. The exhaust gas measuring apparatus according to claim 1 , further comprising: a flow conditioner that is provided on the upstream side of the flow rate sensor in the exhaust gas flow path.

4. An exhaust gas measuring apparatus comprising: an air-fuel ratio sensor provided in an exhaust gas flow path that is connected to a tail pipe of an exhaust pipe of an engine such that the air-fuel ratio sensor is downstream the tail pipe and a catalyst associated with the engine; a temperature sensor that measures temperature of the exhaust gas emitted from the tail pipe; a related data storage part that stores related data that defines a relationship between concentration of each component contained in the exhaust gas and an air-fuel ratio; a temporary concentration calculation part that refers to the related data storage part to calculate temporary H 2 O concentration that is H 2 O concentration corresponding to a measured air-fuel ratio obtained from the air-fuel ratio sensor; and a lost H 2 O calculation part that, on a basis of saturated water vapor concentration at the exhaust gas temperature measured by the temperature sensor and the temporary H 2 O concentration, calculates a lost H 2 O amount that is an amount of H 2 O lost by condensation and the like in a path to a measuring point of the air-fuel ratio sensor to improve measurement accuracy of the air-fuel ratio sensor.

5. The exhaust gas measuring apparatus according to claim 4 , further comprising an air-fuel ratio amendment part that takes into account the lost H 2 O amount to amend the measured air-fuel ratio.

6. The exhaust gas measuring apparatus according to claim 5 , further comprising a component concentration calculation part that refers to the related data storage part to calculate each component concentration corresponding to an amended air-fuel ratio that is the measured air-fuel ratio amended in the air-fuel ratio amendment part.

7. The exhaust gas measuring apparatus according to claim 6 , further comprising: a density calculation part that calculates exhaust gas density on a basis of the each component concentration calculated in the component concentration calculation part; and a fuel consumption calculation part that calculates fuel consumption of the engine on a basis of the exhaust gas density and the amended air-fuel ratio.

8. The exhaust gas measuring apparatus according to claim 4 , wherein the temporary concentration calculation part refers to the related data storage part to calculate respective component concentrations corresponding to the measured air-fuel ratio obtained from the air-fuel ratio sensor, the exhaust gas measuring apparatus further comprising a component concentration calculation part that takes into account the lost H 2 O amount to amend one component concentration of the respective component concentrations calculated by the temporary concentration calculation part, and refers to the related data storage part to calculate the other component concentrations corresponding to the amended one component concentration.

9. The exhaust gas measuring apparatus according to claim 4 , wherein the related data storage part stores the related data for each fuel type.

10. A fuel consumption measuring method for measuring fuel consumption of an engine with use of an exhaust gas flow rate, an air-fuel ratio and exhaust gas density, the fuel consumption measuring method comprising: changing the exhaust gas density on a basis of the air-fuel ratio obtained by an air-fuel ratio sensor and related data indicating a relationship between an air-fuel ratio and exhaust gas density, wherein the air-fuel ratio sensor being is provided in an exhaust gas flow path that is connected to a tail pipe of an exhaust pipe of the engine such that the air-fuel ratio sensor is downstream the tail pipe and a catalyst associated with the engine, and measures a ratio of air to fuel of exhaust gas flowing through the exhaust gas flow path; and calculating the fuel consumption, with use of the exhaust gas flow rate obtained by a flow rate sensor that is provided and measures a flow rate of the exhaust gas flowing through the exhaust gas flow path the air-fuel ratio obtained by the air-fuel ratio sensor and the changed exhaust gas density.